In a 2005 UCLA study, 85% of women said they were "very satisfied" with their romantic partner's size, but 45% of men responded they would prefer their penis size increased and 84% of respondents rated their penis size as average to above average. Penis size is of great concern to many people: some consider having a large penis a mark of masculinity; others are concerned that their penis is too small to satisfy their sexual partner(s). Relying on self-reporting of penis size is problematic, since some patients exaggerate or are unable or unwilling to measure the penis correctly.

Importance for women: No: the most sensitive area of the vagina is the section closest to the outside of a woman's body, which is roughly 10 centimeters in length. Given that the average penis size is above this length, most men should be able to easily reach and stimulate these erotic nerve endings. In an other hand, for many women the efficacy of preliminary period is more important than the penis size itself.